This invention relates to ultrasonic nondestructive testing and more particularly to a pulser circuit for defining interrogating pulses employed in such testing.
Ultrasonic nondestructive evaluation techniques are based on transmission and reflection of acoustic energy in a material under test. Defects in the material are located and evaluated by the characteristics of the energy reflected from them. Examples of systems employing ultrasonic evaluation techniques are shown in U.S. Pat. Nos. 3,690,153, 3,981,184 and 4,004,454. In such systems the interrogating acoustic energy is provided from an electromechanical transducer to a material specimen in the form of pulses. The transducer receives electrical signals from a pulse generator or "pulser" and converts them to acoustic energy.
In many material inspection situations an increased spatial resolution is desirable along the direction of sound propagation in the material. A common limitation in such situations is the duration of the interrogating acoustic pulse. A long pulse creates an uninspectable "dead band" at each interface or discontinuity in the material from which the pulse is reflected. Increased spatial resolution requirements for certain materials and especially for such advanced material systems as composites, powder metallurgy and ceramics require a narrow interrogating acoustic pulse.